The invention relates to a process for the preparation of 1,4-lactones of 3,6-anhydrohexanoic acids from pentahydroxyhexanoic acids.
The 1,4-lactones of 3,6-anhydrohexanoic acids are useful as polyols in the preparation of polyurethanes. See Dirlikov et al., U.S. Pat. No. 4,438,226.
Haworth et al., J. Chem. Soc. I, 88 (1941), disclose a process for the preparation of 1,4-lactones of 3,6-anhydrohexanoic acids. The reference discloses heating a solution of monoacetone 3,6-anhydroglucofuranose in 1N sulfuric acid for 1 hour and then neutralizing the solution with barium carbonate, filtering and evaporating to dryness under reduced pressure to give a syrup which quickly crystallizes. Upon purification, the product is 3,6-anhydroglucose. The anhydroglucose is thereafter oxidized in water with bromine at room temperature for 6 days to afford 3,6-anhydro-1,4-gluconolactone.
Ohle et al., Chem. Ber., 61, 1203 (1928), disclose the preparation of the monoacetone of 3,6-anhydroglucofuranose from glucose in a multistep synthesis.
The preparation of 1,4-lactones of 3,6-anhydrohexanoic acids requires a complicated multistep synthesis. What is needed is a simple and direct process for the preparation of 1,4-lactones of 3,6-anhydrohexanoic acids.